Method of making magnetic alloys



Patented Feb. 23, 1926.

'- UNITED STATES,

VERE 1B. BROWNE, F BRACKENRIDGE, PENNSYLVANIA.

METHOD OF MAKING- MAGNETIC ALLOYS.

No Drawing.

To all whom it may concern:

. tent usually ranging from 3.5% to 4.5%

Be it known that I, VERE B. BROWNE, a citizen of the United States, and a resident of Brackenridge, in the county of Allegheny and the State of Pennsylvania, have made a new and useful Invention in Method of Making Magnetic Alloys, of which the following is a specification.

"This invention relates. to ;a method 'of manufacturing silicon iron.

Silicon iron (so-called silicon steel) is now largely used as a magnetic alloy in the manu facture of certain parts ofelectrical apparatus on account of its high degree of magnetic permeability and low degree of magnetic hysteresis and this invention has particularly to do with the manufacture of silicon ron for use as a magnetic alloy.

The highest grades of silicon iron nowobtainable commercially have a silicon conand a carbon content ranging from 04% to .O8%'. It has been 'known for some time that the value of silicon iron as .a magnetic alloy is not only determined by its silicon content but byits soundness and purity as well. Recent research on this subject has shown that carbon also plays an important part in the value of such material and that a sound carbonless silicon iron of the proper silicon content would have practically no magnetic less.

Small laboratory quantities of silicon iron havin an extremely low carbon content have be and b methodswhicli are wholly impractical or commercial production on a large scale.

In an application for United States Letters Patent filed by me, and serially numbered 16,837, I have disclosed a. method of,

. producing sound silicon iron alloys, that is,

alloys that are free from slag and other solid inclusions such as silica,

An object of the invention of the present application is to provide a method by means of which silicon iron having a silicon'content such as is desirable in a magnetic alloy and acarbon content of not over .03% canbe produced commercially and in large quantities.

A further object of this invention is to provide a method by means of which silicon iron having a silicon content in excess of 3% and a carbon content of not over .03% can be en produced in a vacuum furnace:

Application filed April 2, 1925. Serial No. 20,252.

produced at a relatively large quantities.

- These as well as other objects which will low cost and in be apparent to those skilled in the art to which this invention relates I attain by means of the method and the steps thereof described in the specification and particularly set forth in the claims forming part of this application for Letters Patent.

The method of this invention broadly consists in refining iron in an open hearth pnin an electric arc furnace and in removing from the molten iron as much carbon as is possible by standard methods; then in tapping into a ladle containing a. suflicient quantity of ferro-silicon to produce by exothermic reaction, the heat necessary to maintain the metal at/the correct temperature during the Bessemer blow; then in transferring this siliconized metal to a Bessemer converter and then in' overblowing until substantially all traces of carbon are removed and then in adding the desired amount of silicon to the carbon free iron.

It is generally more diflieult to produce refined low carbon iron in an electric arc furnace than it is in an open hearth furnace,

v because-carbon vapor given'ofl' by the carthat inpracticing my invention I am able' to utilize either an open hearth furnace or an electric arc furnace for refined. iron.

In practicing this method, I refine the metal in the regular way according to standard practice in either 'an open hearth furnace or in an electric arc furnace.

After the metal is refined, I add iron ore to reduce the carbon as in the ordinary practice untilthe reduction reaches the point at whiclrno further reduction is obtained by the addition of more i'rouore. At this stage, I transfer the molten metal to a Bessemer converter, after adding suflicient silicon thereto to generate the necessary amount of heat to keep thelmetal in the converter molten during the blow. The metal is then overblown until practically all of the carbon is removed.

The silicon added-to produce the neces-' sary heat to keep the metal in a molten state as well as some of the iron will, of course, be oxidized. 1

After the carbon has been removed by the producing the overblow the metal is tapped into a ladle and the necessary amount of silicon added thereto to bring the silicon content of the finished material up to the point desired. The silicon is added preferably in the form of ferrosilicon and that which is produced electrically is preferable, since it is possible to obtain such material having a carbon content of not over 2%.

The ferrosilicon is preferably heated and placed in the ladle before the metal is tapped thereinto but if desired it may be added to the metal in a molten state.

'By adding to this practically carbonless iron ferrosilicon containing not over 2% of carbon I can produce silicon iron having a carbon content not greater than 03% and at the same time having a silicon content a high as 4.5%.

Instead of casting directly to the ladle, it is preferable to charge this refined and overblown iron after the necessary silicon has been added thereto in the ladle, into a reservoir as described in my said co-pending application.

The collecting and maintaining of a relatively large bath of this refined alloy in a reservoir in which it is maintained molten by the application of external heat gives the slag and other solid inclusions such as silica an opportunity to float to the surface and combine with the slag on the surface.

While as I have said the iron can be refined in either an open hearth or in an electric arc furnace, I prefer an electric arc furnace, since, in such a furnace, I can maintain a reducing atmosphere and there fore can eliminate all of the sulphur and phosphorus as well as the carbon. I do this y changing the slag on the surface of the bath. Ifirst use an oxidizing slag and thereby remove the phosphorus and a portlon of the carbon. I then remove this slag and replace it by a basic reducing slag and thereby remove the sulphur. After the sulphur is removed, the metal is transferred to the Bessemer converter. The necessary sili-v con is then added and the me-tal'is overblown as described.

I have found that by this method I am able to produce silicon iron that is superior as a magnetic alloy to any heretofore produced commercially. It can be produced at arelatively low cost and in any quantity de-' sired. I also find that I am able, at only a slight increase in cost over the present commercial methods of manufacture, to obtainsilicon iron having a silicon content as high as 4.5% and a carbon content that usually runs well below but never over 03%.

Having thus described my invention,- what I claim is 1. The method of making silicon iron. having a silicon content sufficient to adapt it for use as a magnetic alloy and a carbon content of not over .03%, which consists in refining iron, in reducing the carbon in the refined iron by making additions of iron ore to the bath until no further reduction of carbon is obtained by further additions, in adding sufficient ferro-silicon to produce the necessary heat to mainta-in'the metal molten during a Bessemer blow, in transferring the metal to a Bessemer converter and overblowing to remove the silicon which has been added and substantially all of the remaining carbon, then in transferring the metal to a ladle and in adding thereto the necessary silicon.

2. The method of making silicon iron having a silicon content sufficient to adapt it for use as a magnetic alloy and a carbon content of not over 03%, which consists in refining iron in an open hearth or electric furnace, in reducing the carbon in the refined iron by making additions of iron ore to the bath until no further reduction of carbon is obtained by further additions, in tapping metal from the furnace and in adding sufficient ferro-silicon theretov to produce the heat necessary to maintain the metal molten during a Bessemer blow, in transferring the metal to a Bessemer converter and in overblowing to remove sub-' stantially all of the remaining carbon, then in transferring the metal to a ladle and in adding thereto sufficient ferro-silicon to bring the analysis thereof to the point desired.

3. The method of making silicon iron having a silicon content sufiicient to adapt it for use as a magnetic alloy and a relatively low carbon content, which consists in refining iron in an open hearth or electric arc furnace, in reducing the carbon in the refined iron by adding iron ore thereto, in tapping metal into a ladle and adding thereto suflicient ferro-silicon to produce by exothermic reaction the necessary heat to maintain the metal at the correct temperature during a Bessemer blow, in transferring such metal to a Bessemer converter and then in overblowing until substantially all of the carbon is removed, then in adding to such metal a suflicient quantity of ferrosilicon having a carbon'content of not over 2% to bring the silicon content .of the finished alloy to the point desired- 4. The method of making silicon iron having a silicon content of at least .5% and a carbon content of not over 03%, which consists in refining iron in an oxidizing at mosphere and in utilizing an oxidizing slag to remove the phosphorus and part of the carbon, in removing such slag and replacing the same by a reducing slag whereby the sulphur is removed, then in tapping metal from said furnace into a ladle and adding thereto sufficient-ferro-silicon to pro duce by exo-thermic reaction the necessary carbon content of heat to maintain the metal at the correct temperature during a Bessemer blow, in transferring such'metal to a Bessemer con verter and in overblo'wing the same to remove substantially all of the remaining carbon, then in adding to such 'metal a sufficient quantity of ferro-silicon having a not over 2% to bring the silicon content of the finished alloy to the point desired.

5. The method of making silicon iron having a silicon content sulficient to adapt it for use as a magnetic alloy and a relatively low carbon content, which consists in refining iron in an open hearth or electric arc furnace, in reducing the carbon in the refined won by adding iron ore thereto, in removing sul phur, then in tapping metal from said furnace into a ladle and addin thereto sufficient ferro-silicon to'produce by exo-thermic reaction the necessary heat to maintain the metal at the correct temperature during a Bessemer blow, in transferring such metal to a Bessemer converter and then in overblowing until substantially all of thecar bOn is removed, then in adding to such metal a sufficient quantity of ferro-silicon to bring the silicon content of the finished alloy to the point desired.

In testimony whereof, I have hereunto subscribed my name this 31st day of March, 1925.

VERE B. BROWNE. 

